1. Field
This disclosure relates to plasma processing chambers and, in particular, to plasma processing chambers utilizing inductive and capacitive coupling of RF power to ignite and sustain plasma.
2. Related Art
Plasma chambers that sustain plasma by coupling RF power into a vacuum chamber are well known. Prior art chambers use capacitive coupling, wherein the RF power is applied to two electrodes that form a capacitor. Other prior art chambers utilize inductive coupling, wherein the RF power is applied to a coil or an antenna, which radiates the RF power into the plasma chamber via a dielectric window. Yet other chambers utilize a combination or a hybrid of capacitive and inductive coupling. Examples of such hybrid chambers can be found in, for example, U.S. Pat. Nos. 6,020,686; 6,417,626; 7,780,864; 5,599,396; 6,447,636; and 5,599,396, listed here in no particular order.
One common feature of these hybrid chambers is that the RF power is applied to the inductive antenna and to the lower electrode, such that the bottom electrode serves as the cathode and the top electrode serves as an anode. Such an arrangement requires complex RF wiring to the chuck. Additionally, when the RF coil is provided on top of the chamber, a relatively thick dielectric window is required, in order to overcome the stresses caused by the vacuum inside the chamber.
As can be understood, the prior art relates to fabrication of semiconductor chips. However, recently there has been an increased interest in utilizing plasma processing, such as, e.g., plasma etch, for fabrication of solar cells. The plasma chambers of the prior art fail to satisfy the requirements of plasma processing for solar cells, especially with regards to throughput. A commercially viable plasma chamber for processing solar cells should have at least an order of magnitude higher throughput from standard semiconductor chambers. Accordingly, a new plasma chamber design is needed that fulfills these requirements.